Apple on Wednesday unveiled its first foldable phone, called the iPhone Duo, a device that opens like a book into a wide screen. The announcement marks the biggest change to the iPhone since it was introduced in 2007, and an entry into a category that Samsung has dominated for years.In its announcement, made by Apple’s new CEO John Ternus at the company’s Cupertino, California, headquarters, Apple emphasized that it took time to develop the idea after rivals embraced it years ago.Apple CEO John Ternus speaks during the keynote address at Apple’s “Surprise and Shine” event in Cupertino, Calif., on Wednesday.Benjamin Fanjoy / Getty Images“Others have created foldables that just feel like two phones awkwardly stuck together,” Ternus said in the livestreamed event. He described the Duo as having “a larger display that feels as natural and intuitive as iPad.”Ternus said it was the “largest display ever on an iPhone, while still fitting easily in your pocket.”Apple said the device would sell for a base price of $1,999. Preorders would start Oct. 16, and the device will be available at stores on Oct. 23, the company said.Once opened, the double-wide screen is 50% larger than the size of the iPhone Pro Max and measures 7.6 inches on the diagonal, said Greg Joswiak, Apple’s senior vice president for worldwide marketing. He said the device is made of titanium, has speakers on the top and the bottom, and initially will come in two colors: “star white” and “night sky.”